Microphone Assembly Digital Feedback Loop for Low-Frequency Overload

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Portable communication devices face challenges in achieving high sound quality and robustness for microphone assemblies due to saturation and non-linearity issues in signal processing circuits, particularly at high sound pressure levels, which result in overload and distortion.

Innovation Solution

A microphone assembly with a processing circuit that includes an analog-to-digital converter, a digital loop filter, and a digital-to-analog converter to create a feedback loop, which filters and adjusts the frequency response, preventing low-frequency overload and distortion by combining the microphone signal with an analog feedback signal at the transducer output.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the microphone assembly uses conventional signal processing circuits with preamplifiers and buffers, then the device can process microphone signals, but saturation and non-linearity occur at high sound pressure levels causing overload and distortion

Engineering Contradiction:

Improvesignal processing robustnessVSAvoidoverload and distortion

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent implements a digital feedback loop where the digital microphone signal is processed through a digital loop filter and converted back to analog via a DAC, then fed back to the transducer output. This feedback mechanism actively controls the frequency response and prevents saturation by adjusting the signal path based on detected conditions, thereby eliminating overload and distortion while maintaining processing robustness

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent replaces conventional analog signal processing mechanisms with a digital processing approach. By converting the microphone signal to digital format using an ADC and processing it through digital filters and algorithms, the system achieves linear signal processing without the saturation issues inherent in analog amplification circuits, thereby preventing overload and distortion

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Quantity of substance

If the microphone assembly processes high sound pressure level signals, then the dynamic range is increased, but saturation of active amplification elements occurs causing non-linearity

Engineering Contradiction:

Improvesignal dynamic rangeVSAvoidsignal linearity

Core Design Contradiction:

Quantity of substanceVSStability of the object's composition

Solution Approach 1:

The patent substitutes analog amplification with digital signal processing. The ADC converts the analog microphone signal to digital format, where subsequent processing occurs through digital filters and algorithms rather than analog amplifiers. This digital approach maintains signal linearity across the full dynamic range without the saturation limitations of active amplification elements

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the operating parameters of the signal processing system by implementing a digital feedback loop with an adjustable transfer function. This allows dynamic adjustment of processing characteristics based on signal conditions, maintaining optimal linearity and preventing saturation even at high sound pressure levels while preserving the full dynamic range

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This solution effectively suppresses low-frequency components, reducing the maximum signal level handled by the preamplifier and buffer, thereby preventing overload and distortion, and allows for accurate control of the frequency response, improving sound quality and stability in portable devices.

Implementation Method 1

a transducer configured to convert sound into a microphone signal

Methodology Applied

Scientific EffectAcoustic transduction:

Implementation Method 2

a digital loop filter which includes an adjustable or fixed transfer function, the digital loop filter being configured to receive and filter the digital microphone signal

Methodology Applied

Scientific EffectDigital signal filtering: Filter (electronic)

Implementation Method 3

a digital-to-analog converter (DAC) configured to convert the first digital feedback signal into a corresponding analog feedback signal

Methodology Applied

Scientific EffectDigital-to-analog conversion:

Implementation Method 4

a summing node at the transducer output configured to combine the microphone signal and the analog feedback signal

Methodology Applied

Scientific EffectSignal superposition:

Data Source

PatentUS11323805B2Microphone assembly with digital feedback loop

Publication Date: 2022.05.03 KNOWLES ELECTRONICS LLC

AI summary

A microphone assembly includes a transducer element and a processing circuit. The processing circuit includes an analog-to-digital converter (ADC) configured to receive, sample and quantize a microphone signal generated by the transducer element to generate a corresponding digital microphone signal. The processing circuit includes a feedback path including a digital loop filter configured to receive and filter the digital microphone signal to provide a first digital feedback signal and a digital-to-analog converter (DAC) configured to convert the first digital feedback signal into a corresponding analog feedback signal. The processing circuit additionally includes a summing node at the transducer output configured to combine the microphone signal and the analog feedback signal.